The present invention relates generally to a method and apparatus for transferring heat from an electronic component. More particularly, it relates to methods and apparatus for mounting graphite-based heat transfer apparatus upon electronic modules in a manner for reducing material and thermal degradations of the former.
Electronic components, such as microprocessors and integrated circuits, must operate within certain specified temperature ranges to perform efficiently. Excessive heat, however, degrades their performance, reliability, life expectancy, and even causes failure. For controlling excessive heat, heat sinks are a typical thermal management protocol. It is not uncommon to have heat sinks formed with fins or other similar structures to increase the surface area of the heat sink, whereby air can pass to thereby enhancing heat dissipation. Typically, heat sinks are formed of metals, such as copper or aluminum, because they readily absorb heat and transfer it about their entire structure.
Recently, graphite-based materials have been used for heat sinks, and they offer many advantages over the metallic kinds. For instance, the anisotropic nature of graphite allows preferential direction of heat from an external surface of an electronic component to the heat dissipation fins. This is compared to the isotropic nature of metallic heat sinks, wherein the heat transmitted by the heat sink is distributed about the structure rather than being directed to the fins; which are the most efficient heat dissipation area. Graphite materials have the further advantage of relatively low density, and thus relatively low weight, whereby a graphite apparatus of the same approximate size and volume of a copper apparatus will weigh significantly less. In addition, a significant advantage of graphite over metals can be expressed in terms of improved thermal conductivity. Therefore, graphite is distinctly advantageous.
Despite such advantages, however, limitations on its use nevertheless exist. Shortcomings are present, for example, in environments requiring relatively high actuating load forces being applied thereto. These are due primarily to the tendency of graphite to crack and fracture when subjected to heavy loading. One example is when attempting to mount a graphite heat sink on a multi-chip module (MCM), wherein forces of several hundred pounds are required to be applied to the heat sink for mounting purposes. Such cracking can cause corresponding cracking in the thermal paste at the thermal interface, thereby lessening thermal conductivity. These constraints are compounded by the requirement that the graphite heat sink be compliant to the shape of prior heat sinks used in a MCM environment.
Therefore, without the ability for effectively transferring heat from an electronic component, especially in an MCM environment, by using graphite-based heat sinks in a manner that avoids mechanical and thermal degradations, the true potential of using such heat sinks is not entirely realized.